In general, sliding bearings fitting on a shaft for rotation, movement, and support are used for various joints throughout construction machines, hydraulic equipment, and machines. In the sliding bearing, a lubricant is supplied to the sliding contact surface between a shaft and the bearings supporting the shaft to prevent inner friction. The lubricant is periodically supplied and forms a thin oil layer by flowing on the sliding contact surface between the shaft and the sliding bearing, as the shaft rotates and moves.
In the sliding bearing, the oil layer may partially break when the apparatus stops or operates or variable load is applied to the apparatus from the outside, and the lubricant is exhausted and the oil layer becomes insufficient, when the sliding bearing is used for a predetermined period of time. As described above, when the oil layer is locally disconnected or insufficient, the contact pressure between the shaft and the sliding bearing increases and scorching and sticking is caused between the shaft and the sliding bearing by friction heat due to the contact pressure, thereby increasing the amount of wear.
The conditions of surface pressure and speed of the sliding bearing that is used for various joints with the phenomenon are very various and there is a limit in fitting the conditions of surface pressure and speed within all ranges for one type of sliding bearing to use. Therefore, it is important to reduce scorching and sticking and wear between the shaft and the bearing by disposing an optimal applicable product in the right place within a predetermined range of surface pressure and speed. Further, it is necessary to increase a supply time for the sliding bearing to keep the lubrication effect.
An example of a bearing device configured to prevent scorching and sticking between the shaft and the sliding bearing is disclosed in Korean Patent Application Laid-Open No. 2006-0070264. In this configuration, a shaft is formed in a hollow body with a space to store a lubricant therein such that the storage amount of lubricant increases. In the bearing device, a plurality of holes for supplying a lubricant which are connected to the hollow body is formed in the shaft. The storage for a lubricant formed in the shaft, as described above, increases the time until the lubricant is exhausted, by increasing the amount of lubricant that is supplied to the sliding contact surface, and accordingly, the time of supplying the lubricant increases. However, since the shaft is formed in a hollow body, the rigidity is insufficient in some cases.
Another example of a bearing device configured to prevent scorching and sticking between the shaft and the sliding bearing is disclosed in Korean Patent Application Laid-Open No. 1999-0082076. The bearing device disclosed in the patent has a lubricant pocket on the surface sliding in contact with the shaft, in which the depth is 0.03 mm to 0.3 mm and the ratio of the pocket area to the pocket depth is about 10 to 40 mm. When a lubricant pocket is formed on the sliding contact surface, as described above, the lubricant in the pocket is supplied to the sliding contact surface in sliding, such that local oil layer cut is prevented. However, the depth of the lubricant storage is too small in this configuration, such that the amount of lubricant that can be stored is small and the supply period cannot be extended.
It is impossible to ensure scorching-sticking resistance and wear resistance by extending the supply time even in the bearing devices configured to prevent scorching-sticking on the sliding bearings described above, such that the oil layer may still become insufficient or may be broken within a short time.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.